Servint (CPanel)
This is a standard CPanel host.
Follow the standard CPanel installation as shown in the tutorial video Installing on CPanel Hosting in the video library.
Cron task
Use the standard CPanel cron definition.
php-cli /path/to/your/public_html/a/a.php cli/auto
Example
php-cli /home/mylogin/public_html/a/a.php cli/auto